Apparatus for drilling holes in underground formations



' Oct. 1, 1963 1. HAVENAAR 3,105,563

APPARATUS FOR DRILLING HOLES IN UNDERGROUND FORMATIONS Filed July 6. 1 960 WWWA 'W/////// INVENTOR:

IZAK HAVENAAR BY.

United. rates l atent @fihce Kiel 3,105,563 APPARATU? F011 DRUJLENG HflLES IN UNDERGRGUND FORMATEONS Izaak Havenaar, Amsterdam, Netherlands, assignor to Shell Oil Company, New York, N.Y., a corporation of Delaware Filed July 6, 196% er. No. 41,129 Claims priority, application Belgium July 18, 1959 2 (Ilaims. (Ql. 175-337) The invention relates to an apparatus for drilling holes in underground formations, which apparatus is provided with parts which rotate relative to each other and are in terconnected by means of at least one bearing, and with a drillin -mud supply and discharge.

The formations drilled by these apparatuses usually consist of rocks. These rocks are crushed by means of the cutters (for example teeth) of the drilling apparatus, which cutters are made of wear-resistant material and rotate on the rock under a hoa y load. These cutters are cooled and cleaned by means of drilling mud supplied through a nozzle. In order to prevent the drilled hole from being compressed by the pressures prevailing in the rocks, clay and/ or other weighting material is added to the drilling mud. This material added to the drilling mud also forms a filter layer on the inside of the drilling hole when porous rocks are drilled, as a result of which less of Water from the drilling mud is prevented. if desired, materials having a particularly high sealing effect may be added to the drilling mud.

A drawback of such additions to the drilling mud is that they penetrate into the bearing spaces between the parts rotating relative to each other and cause very rapid wear of the bearings housed in these spaces.

As is known the drilling mud supplied through the drill pipe and the bit to the bottom of the hole is returned through the annular space between the drill pipe and the wall of the bore hole, the crushed rock being carried upward. The cuttings are separated from the drilling mud on the surface, after which the drilling mud thus cleaned can be used again.

However, when the drilling mud is cleaned the very finest particles of the cuttings are left behind in the mud and these particles increase the wearing efiect of the mud penetrating into the bearing spaces.

As a result of this heavy wear the bearings of the drilling apparatus are in certain cases worn sooner than the remaining parts thereof. The drilling apparatus then has to be replaced at a time when it is not entirely worn, and this is very undesirable as it greatly increases the drilling costs per metre of rock dril ed.

Drilling apparatuses provided with parts which rotate relative to each other are, for example, drilling or core bits having cylindrical or conical roller cutters rotating about fixed pins. Reamer bits may also be provided with rotating reamers arranged rotatingly round fixed pins.

Bearings are also arranged between rotating parts in drilling apparatuses in which the driving motor is mounted immediately above the drilling members.

In all these cases these hearings, which are in the form of ball, roller or bush bearings, are in contact with the drilling mud during drilling, as a result of which, has already observed above, there will be rapid wear of the bearings and the bearing surfaces of the rotating parts.

The object of the invention is to obviate this difiiculty, to which end according to the invention a filter is arranged in the drilling apparatus between the supply and discharge of the drilling mud in such a way that during operation the mud flowing through the drill ng apparatus fiows along one side of the filter, and the space adjacent to the other side of the filter communicates with the bearing space between the parts rotating relative to each other.

The filter is preferably of a cylindrical design, the space inside the filter establishing communication between the supply and discharge of drilling mud and the space surrounding the outside of the filter communicating with the said bearing space.

The drilling apparatus may be formed by a drilling bit provided with projections on which pins are mounted round which roller cutters are rotatably arranged, and may also be provided with at least one nozzle through which drilling mud is discharged during operation. Like the above-described drilling apparatus, the drilling bit is also provided with a filter, the side not in contact with the mud fiowing past communicating with the space between the pins and the roller cutters via a channel system arranged in the body of the drilling bit, the projections and the pins.

In all these constructions some of the mud flowing through the drilling bit is passed through the filter, freed from the entrained particles and supplied entirely clean via a channel system to the bear-ing spaces between the parts rotating relative to each other. The bearing spaces are continuously flushed with the cleaned drilling mud, as a result of which particles prevented from penetrating into the bearing spaces.

Since the drilling mud flowing through the drilling apparatus flows along one side of the filter the surface of the filter is continuously cleaned, thereby preventing the formation of a thick filter cake which would excessively reduce the flow through the filter.

The filter body may be made of a permeable mass such as porous metal, porous ceramic material or consolidated sand. The latter material is obtained by cementing granules of sand with a resin while retaining a certain permeability. The invention is not, however, limited to the use of these filter materials. Any other type of filter materials, such as nylon fabric may :be used, provided they are capable of removing particles from the drilling mud up to a size of a few microns.

The invention will be further described with reference to the drawing in which a roller bit is shown by way of example.

The drilling apparatus is here constructed of two parts 1 and 2, part 1 forming the actual drilling bit provided with pins 3, bearings 4, roller cutters S and at least one nozzle 6, and part 2 forming a cylindrical extension piece of the shaft 7 of part 1 which is secured thereto by means of screw thread 8. Part 2 consists of two parts, pipe section 2' and nipple 2" connected by means of a screw thread, the top of which part 2 is provided with screw thread 9 which can be connected to the bottom of the drilling string (not shown). if desired, some drill collars may also be arranged between the drill pipe (not shown in the drawing) and the screw thread 9 if it is desired to increase the pressure exerted on the bit.

The hollow space ill in the body of the drilling bit is provided with a supply opening 11 which immediately communicates with the interior of the drilling string not shown, consisting of drill pipes which, if desired, may be supplemented by drill collars. The bottom of the space 10 communicates with the bore hole via the nozzles 6. The tubular filter body 12 the outside of which is surrounded by the annular space 13, is mounted in the pipe section 2'. Communication between the space 19 and space 13 can only be established via the filter body 12, since the connection between filter body 12 and the parts 1 and 2 of the bit body is sealed by suitable means (14).

A channel system 15 communicates with the annular space 13, which system leads to the bearing space 16 between the pins 3 and the roller cutters 5. In the embodiment shown in the drawing the bearing 4 is designed as a roller and ball bearing, but the invention is not limited to this use. Bearings consisting of bushings may also charged with drilling mud are be protected from excess wear in the manner according to the invention.

' The bit now operates as follows. Before being lowered into the 'bore hole the bit is secured to the bottom of a drill pipe (not shown) by means of the screw thread 9 By screwing on other drill pi es a drilling string is formed by means of which the drilling bit is placed on-v the bottom of the bore hole. The drilling string is then rotated, and as a result of the pressure exerted on the drilling bit by a part of the weight of the drilling string the cutters of the rollers crush the rock on the bottom or" the bore hole. At the same time drilling mud is supplied through the interior of the drilling string, which mud enters the hollow space 10 of the bit via the supply opening 11 and then flows along the surfaces of the filter body 32 to the nozzle 6 whence it is jetted with great force against the roller cutters 5 and/ or the bottom of the bore hole.

Some of the mud flowing along the wall of the filter body is, however, filtered in this filter and the filtrate is led to the bearing spaces 16 via the space 13 and the channel system 15. Since the filtrate flows through the bearing spaces 16 and escapes via the slits between the pins 3 and the rollers 5, no mud charged with particles can penetrate from the outside of the bit into the bearing spaces 16. Consequently, there is a substantial reduction in the wear of the bearing 4.

' The amount of filtrate withdrawn via the bearing spaces depends on the total amount of mud supplied and is also a function of the relationship between the resistances to which the flow is subject in the jet nozzles 6 on the one hand, and in the filter 12, the space 13, the channel system 15 and the bearing spaces 15 on the other. When a filter showing a high resistance to flow is used, jet nozzles 6 should be used of which the resistance to flow is not too small, as otherwise practically the whole amount of drilling mud will fiow through the nozzles 6 and the amount of filtrate passed through the filter, the space 13, the channel system 15 and the bearing spaces 16 is too small to prevent drilling mud charged ith particles from penetrating into the bearing spaces 16.

Accretion of filter cake deposited on the wall of the filter body is prevented by the highly erosive effect exerted by the mud flowing from the supply opening 11 to the nozzles 6, thereby constantly ensuring the filtering efiect of the filter.

If desired, the bit body may be made of one piece, in which case the filter 12 is entirely housed in the extended shaft 7 of this body. It is, however, preferred to divide the body into two parts 1 and 2, as shown in the drawing, since after the cutters of the rollers have become worn the part 2 may be detached from part 1 without much difilculty and then used again in a new bit.

It is also possible to house the filter 12 in a drill collar or drill pipe which isthen connected to the bit in 4% the normal manner. An annular groove for establishing the communication between the two parts of the channel system 15 is then provided in the coupling.

The use of the invention is not limited to the protection of hearings in drill bits. Any type of bearing arranged between drilling apparatus parts rotating relative to each other may be protected against excessive wear in the manner indicated.

If desired, the cylindrical filter 12 may be composed of several cylindrical parts, a suitable sealing being provided etween the contact surfaces or" these parts.

Stops may also be provided in the annular space 13 for centering and supporting the filter 12 or the parts thereof.

The filter is preferably made of permeable material which has great resistance to wear. This material is preferably porous metal, permeable ceramic material or consolidated sand. The latter material may be obtained by cementing together grains of sand with a resin while retaining a certain desired permeability.

I claim:

1. In a well drill apparatus provided with rotatablymounted cutter wheels (at) a bit supporting said cutter wheels through bearing elements,

(b) a pipe section secured to said bit and extending upwardly therefrom in fluid communication with a mud-supplying drill string,

(c) an elongated tubular filter element disposed longitudinally within the pipe section and bit, said tubular filter being of a size whereby an annular space is formed between said filter and said pipe section,

(cl) said bit having passages extending therethrough and in communication with said annular space whereby a portion of the mud supplied to the drill string passes through the filter element into the bearing elements while the balance of the mud flushes over the fi ter onto the cutter wheels of the bit, and

(e) a nipple connecting the pipe section to the drill string, said nipple having a bore of a diameter equal to that of the bore of the tubular filter, whereby the filter does not interfere with the flow from the nipple.

2. An apparatus according to claim 1 including seal elements interposed between the ends of the filter and the nipple and the bit members, whereby unfiltered mud Within the filter cannot communicate with the filtered mud in the annular space disposed around the filter.

References Qited in the file of this patent UNITED STATES PATENTS Swart Apr. 7, 1959 

1. IN A WELL DRILL APPARATUS PROVIDED WITH ROTATABLYMOUNTED CUTTER WHEELS (A) A BIT SUPPORTING SAID CUTTER WHEELS THROUGH BEARING ELEMENTS, (B) A PIPE SECTION SECURED TO SAID BIT AND EXTENDING UPWARDLY THEREFROM IN FLUID COMMUNICATION WITH A MUD-SUPPLYING DRILL STRIP, (C) AN ELONGATED TUBULAR FILTER ELEMENT DISPOSED LONGITUDINALLY WITHIN THE PIPE SECTION AND BIT, AND TUBULAR FILTER BEING OF A SIZE WHEREBY AN ANNULAR SPACE IS FORMED BETWEEN SAID FILTER AND SAID PIPE SECTION, (D) SAID BIT HAVING PASSAGES EXTENDING THERETHROUGH AND IN COMMUNICATION WITH SAID ANNULAR SPACE WHEREBY A PORTION OF THE MUD SUPPLIED TO THE DRILL STRIP PASSES THROUGH THE FLITER ELEMENT INTO THE BEARING ELEMENTS WHILE THE BALANCE OF THE MUD FLUSHES OVER THE FILTER ONTO THE CUTTER WHEELS OF THE BIT, AND (E) A NIPPLE CONNECTING THE PIPE SECTION TO THE DRILL STRIP, SAID NIPPLE HAVING A BORE OF A DIAMETER EQUAL TO THAT OF THE BORE OF THE TUBULAR FILTER, WHEREBY THE FILTER DOES NOT INTERFERE WITH THE FLOW FROM THE NIPPLE. 